Electrolyte Supplement Guide: Hydration, Mineral Replenishment, and Muscle Cramp Prevention During Exercise

Electrolytes are minerals that exist as ions in bodily fluids and transmit electrical signals. Key electrolytes include: Sodium (Na⁺), involved in regulating body fluid volume, enhancing intestinal water absorption, and nerve signal transmission. Potassium (K⁺), the primary intracellular electrolyte, essential for muscle contraction, cardiac electrical activity, and nerve conduction. Magnesium (Mg²⁺), involved in muscle relaxation, enzyme cofactor activity, and ATP energy metabolism. Chloride (Cl⁻), which works with sodium to maintain fluid balance. These are lost through sweating, making conscious replenishment necessary during prolonged exercise.

A review by Shirreffs & Sawka (2011) confirmed that dehydration exceeding 2% of body weight significantly impairs aerobic capacity, cognitive function, and thermoregulation. For a 70-kg person, this corresponds to approximately 1.4 kg of fluid loss — an easily achievable threshold during more than an hour of intense exercise. By the time thirst is felt, dehydration of approximately 1% may already have occurred, making thirst-guided hydration potentially inadequate. Pre-exercise hydration (pre-hydration) and regular replenishment during exercise are recommended.

2% of body weight

Dehydration level at which performance begins to decline

For moderate exercise under 60 minutes, water is generally sufficient. For intense exercise exceeding 60 minutes, electrolyte drinks containing sodium outperform water alone for several reasons: sodium enhances intestinal water absorption, maintains the desire to drink (stimulating drinking behavior), and is needed to restore lost fluid volume. Sports drinks combining carbohydrates and electrolytes also accelerate intestinal absorption (via cotransport mechanisms). However, habitually consuming electrolyte drinks during short exercise or daily life may lead to excessive sugar intake, so caution is warranted.

60 minutes

Exercise duration threshold where electrolyte replenishment becomes particularly beneficial

Individual sweat rates and sweat sodium concentrations vary considerably (400–2,000 mg/L), making universal supplementation recommendations difficult. As a general guideline, sodium lost through sweat during one hour of exercise is approximately 500–2,000 mg, and potassium approximately 200–600 mg. Conscious sodium replenishment becomes important for long-distance runners and training in hot weather. A simple way to estimate your own sweat rate is to measure body weight before and after exercise — a 1 kg difference roughly equals 1 liter of sweat loss. Basing mineral intake on diet (potassium from bananas, sodium from salt, etc.) and supplementing as needed is a practical approach.

400–2,000 mg/L

Individual variation in sweat sodium concentration